Australia: We all know that fish and chips wouldn't be the same without salt. However, scientists have now claimed that the yearning for salt stimulates the brain like addiction to hard drugs or cigarettes.

They found that the craving triggers the same genes, brain cells and brain connections.

The finding could help explain why many find it so hard to cut back on salt, despite warnings about dangers to blood pressure and heart health.

For the study, Australian and American scientists kept some mice on low-salt diets and gave others a salt drip.

Activity in the creatures' brains was then compared with that in mice fed normally. They also studied the brains of mice that had been starved of salt for three days and then given salty water to drink freely.

When the rodents were in need of salt, brain cells made proteins more usually linked to addiction tosubstances such as heroin, cocaine and nicotine.

"In this study we have demonstrated that one classic instinct, the hunger for salt, is providing neural organisation that subserves addiction to opiates and cocaine," a daily quoted Prof Derek Denton, of the University of Melbourne, as saying.

The study also revealed that after salt was taken, the brain believes it has received its fix well before it should be physically possible.

In other words, the changes caused by salt cravings disappeared well before the salt could have left the gut, entered the blood and got to the brain.

"It was amazing to see that the genes that were set 'off' by the loss of sodium were already beginning to get back to the original state within ten minutes," said Prof Denton.

"It is an evolutionary mechanism of high survival value because when an animal is depleted of water or salt it can drink what it needs in five to ten minutes and get out which makes it less susceptible to predators,' he added.

The researchers said that the importance of salt to overall health means that cravings for it form 'an ancient instinct' deeply embedded in the brain. This may explain why we find salty foods so tasty.

The study appears in the journal Proceedings of the National Academy of Sciences.